The present invention relates to a diaphragm valve, and especially to an electromagnetic permeable-shell-free diaphragm valve.
The 07/082,086 application discloses an automatic ink jet marking system which comprises a nozzle set, an ink supply device, and a microcomputor. The valve is installed in the nozzle set for switching the flow of the ink which is pressurized by compressed air. That is, the ink will be pumped toward a nozzle when the valve is actuated to open, and the flow of the ink will be obstructed when the valve is actuated to close.
The U.S. Pat. No. 4,378,564 titled "Ink Jet Printing Apparatus and Process" issued to Printos B.V. of N.L., Naarden, Netherlands on Mar. 29, 1983 discloses a solenoid valve shown in FIG. 7, wherein the coil 10 incorporates with the spring 12 to actuate the valve stem 11 to move rightward and leftward, and accordingly the pressurized ink flows toward a nozzle through the path shown by the arrows A and A'.
The 07/082,086 application also discloses an electromagnetic valve shown in FIG. 6, wherein the coil 20 incorporates with the spring 22 to actuate the valve stem 21 to move rightward and leftward, and accordingly the pressurized ink flows toward a nozzle along the direction shown by the arrows B and B', and the urging force induced by the spring 22, which pushes the valve stem 21 toward the valve seat 26, is substantially adjusted by means of screwing the bolt 23 in or out of the inner hole of the sleeve member 24. Similarly, the stroke of the stem 21 can be adjusted by screwing the sleeve member 24 in or out of the shell 25.
Both of the two valves described above are constructed in such a manner that the valve stem is immersed in the ink, and the reciprocating motions of the valve stem are impeded when the ink is dehydrated.
Furthermore, the construction of the valve disclosed in the 07/082,086 application is too complicated to be produced more cheaply or to be made smaller.
In addition, the high-frequency response of the two valves described above is poor due to the bouncing phenomenon induced between the valve seat and the rigid end portion of the valve stem, and the quantity of the ink jetted out will fluctuate time after time when bouncing occurs, so that it is difficult to facilitate the valves to operate at high frequency.
Besides, the valve shell enclosing the coil will hinder the dissipation of the heat produced by the coil during operation, and heating will change the quality of the ink.